1. Field of the Invention
This invention relates to stackable gravity-discharge portable hoppers for handling, storing and dispensing bulk materials, and more particularly concerns hoppers in sanitationconscious or hygienic environments, for example, for use with dry flowables such as capsules and tablets in the pharmaceutical industry.
2. Description of the Prior Art
Portable or mobile hoppers of the prior art have used a separate base or stand to support stainless steel or, later, a synthetic plastic hopper. Typically, such supporting bases or stands were made of stainless steel. More recently, these supporting stands have been made of molded seamless double wall plastic construction. The separate hopper and separate support stand must be cleaned, and cleaning two pieces of equipment is more time-consuming and expensive.
Another problem with separate hopper and base combinations is that if the hopper-base combinations are stacked four or five high, when an operator of a forklift attempts to move a stacked hopper-base, he cannot see the lid or manway of the hopper below, and he has to guess how high he must raise the tines of his forklift to slip under the upper hopper-base and not damage the lid or manway of the lower hopper. The operator may misjudge the height at which to place the tines of his forklift and may damage the lid and manway of the hopper that is underneath the hopper he wishes to move.
Also, the forklift operator must judge how far apart to space the tines of his forklift truck so it does not damage the iris valve or slide gate valve that may be located on the bottom of the upper hopper. If the operator of a forklift does not space the tines of his forklift truck far enough apart, the tines may cause damage to the iris valve and may even damage the bottom wall of the upper hopper.
Another problem is that it has been difficult to gain access to the inside of portable hoppers positioned under a machine, such as a coating machine or tablet forming machine, because the only way to gain access to the interior may be through a manway formed in the center of the hopper cover which may be difficult to reach since it is under the center of the machine and may require additional conveyance apparatus.
Another problem is that it is difficult to store hydroscopic material in various known hoppers since the covers for these hoppers are not moistureproof.
Another problem with various known hoppers is that emptying them requires that the contents of the hopper be exposed to the surrounding environment, which is unacceptable in the pharmaceutical industry.